Example Projects:
Electrohydraulic Prosthetic Ankle
Fully powered prosthetic ankles are significantly larger and heavier than the passive devices typically used clinically. The size of fully powered ankles can largely be attributed to the motors and transmissions required to provide the large burst of positive power seen at the end of the stance phase of walking. However, significant biomechanical benefit may still be provided to patients without this large burst of power (and subsequent size penalty).
The goal of this project was to develop a prosthetic ankle that forgoes significant positive power delivery to minimize size and weight while still providing significant biomechanical benefit to patients across multiple activities. This device leverages durable passive components in conjunction with small motors to modulate the passive behavior of the device in response to the user’s needs. This design uses a novel hydraulic cylinder actuator in parallel with an electromechanical linear drive system to provide both passive and powered actuation. This project involved the development of a custom embedded system, actuators (utilizing both hydraulics and electric motors), sensors, and onboard controls.
More detail can be found in our peer-reviewed publication here.
Swing Assist Prosthetic Knee
Currently available prosthetic knees provide a high resistance during weight-bearing and a low resistance during the swing phase of gait. The high resistance during weight-bearing prevents the knee from buckling under load while the low swing-phase resistance allows the device to react to the intentions of the user and provides a natural swing-phase knee motion. However, due to the low resistance of the knee during swing, it is highly susceptible to external perturbations like scuffing the ground or bumping a curb. Due to this limitation of current prosthetic knees, stumble and scuff events often lead to falls.
The goal of this project was to develop a prosthetic knee that maintains the beneficial characteristics of current prosthetic knees while addressing the issue of frequent falls as a result of swing-phase perturbations. To this end, a swing-assist prosthetic knee was designed that leverages a passive mechanism for weight-bearing support and a highly backdrivable electromechanical drive system for swing-phase assistance. This active drive unit allows for low resistance swing phase behavior as well as the ability to actively reject scuff or stumble perturbations, thereby preventing falls. This project involved the development of a custom embedded system, actuators (utilizing both hydraulics and electric motors), sensors, and onboard controls.
More detail can be found in our peer-reviewed publication here.
Compliant and Low Profile Prosthetic Foot
Low-profile prosthetic feet are typically stiff relative to feet not specifically designed to minimize build height. This problem is due to fundamental limitations associated with their designs. These stiff low-profile feet mean that patients are forced to use stiff feet that have both low energy return and a high rate of mechanical failure.
To address this issue, we have developed a novel low-profile foot with optimized geometry in order to achieve compliant behavior without sacrificing strength. This new foot achieves over twice the energy storage density of standard feet, allowing it to be high performance, compact, and lightweight.
The novel low-profile foot can also be manufactured at a low cost. Instead of using labor-intensive composite layup techniques to make the foot, this novel foot is constructed from flat sheet stock that can be cut using a variety of low cost manufacturing techniques.
More detail can be found in our peer-reviewed publication here.
Passive Ankle with Swing Phase Dorsiflexion
Prosthesis users suffer from frequent falls. This high fall rate can partially be attributed to scuffs and stumbles that result from a lack of clearance between the foot and the ground during swing phase of walking. Some commercial devices address this issue by lifting the toe (dorsiflexing) during swing phase, but do so at the cost of size, weight, complexity, and stance phase energy return.
To address this clinical problem, we have developed a passive prosthetic ankle joint (shown here paired with our custom compliant foot) that dorsiflexes during swing without suffering from the drawbacks of other commercial alternatives. The ankle provides plantarflexion at heel strike, energy storage and return during stance, and dorsiflexion during swing.
The biomechanical features described above are enabled by a novel mechanism that provides a geometric lock whenever the user applies their weight to the system (during stance phase). This novel locking approach provides substantial durability and reliability advantages over other locking mechanisms such as clutches or latches.
More detail can be found in our peer-reviewed publication here.
